Having accumulated a set of octal tube base clamps, it’s now a matter of selecting the proper clamp for each tube:
The process of shell-drilling the tube base, drilling the hard drive platter, printing a tube socket and case, wiring up the Arduino and base LED, then assembling the whole thing requires a bit of manual labor, assisted by some moderately exotic shop machinery.
The getter flash atop this small 6H6GT dual diode tube rules out a cap and there’s not enough space for a side light:
Fortunately, the base LED completely lights the internal glass:
The slowly changing color would make a fine night light:
It must be Art!
The Smell of Molten Projects in the Morning 
Just out of curiosity… what are you going to do with all these lamps? By my account you’ve got quite a collection by now :)
There’s a Mini Maker Faire coming up next month. I’ve done 3D printing twice and showed off the plotter, soooo this could be the new hotness.
If anybody offers to buy ’em, it’ll count it as market research!
The 6H6 is a cute little tube, unfortunately the metal version is much more common if less æsthetic. The old pinch seal types work particularly well for bottom lighting, as the seal operates as a light guide and diffuser.
Everything so far (*) has come from the Box o’ Hollow State Electronics: what you see is what I got. The few metal cans in the pile have settled to the bottom, never to be seen again.
(*) I fell for a quartet of 21HB5A tubes from eBay in a moment of weakness.